-enni-, -ennial, -ennium

(Latin: year, years)

tricentennial

1. Relating to or completing a period of 300 years.
2. A space of 300 hundred years.
3. A reference to 300 years or a period of 300 years.
4. A tercentenary event or celebration.

triennial

1. Existing or lasting for three years, three-years; changed every three years.
2. Recurring every three years.
3. A commemoration or celebration of an event that occurred three years earlier; a third anniversary.

triennially

1. Referring to a third anniversary.
2. Descriptive of something which appears or occurs every three years.
3. Referring to a period of three years; triennium.